Protein and cell patterning in closed polymer channels by photoimmobilizing proteins on photografted poly(ethylene glycol) diacrylate

Definable surface chemistry is essential for many applications of microfluidic polymer systems. However, small cross-section channels with a high surface to volume ratio enhance passive adsorption of molecules that depletes active molecules in solution and contaminates the channel surface. Here, we present a one-step photochemical process to coat the inner surfaces of closed microfluidic channels with a nanometer thick layer of poly(ethylene glycol) (PEG), well known to strongly reduce non-specific adsorption, using only commercially available reagents in an aqueous environment. The coating consists of PEG diacrylate (PEGDA) covalently grafted to polymer surfaces via UV light activation of the water soluble photoinitiator benzoyl benzylamine, a benzophenone derivative. The PEGDA coating was shown to efficiently limit the adsorption of antibodies and other proteins to <5% of the adsorbed amount on uncoated polymer surfaces. The coating could also efficiently suppress the adhesion of mammalian cells as demonstrated using the HT-29 cancer cell line. In a subsequent equivalent process step, protein in aqueous solution could be anchored onto the PEGDA coating in spatially defined patterns with a resolution of <15 μm using an inverted microscope as a projection lithography system. Surface patterns of the cell binding protein fibronectin were photochemically defined inside a closed microfluidic device that was initially homogeneously coated by PEGDA. The resulting fibronectin patterns were shown to greatly improve cell adhesion compared to unexposed areas. This method opens for easy surface modification of closed microfluidic systems through combining a low protein binding PEG-based coating with spatially defined protein patterns of interest

Influence of Introgression and Geological Processes on Phylogenetic Relationships of Western North American Mountain Suckers (Pantosteus, Catostomidae)

Intense geological activity caused major topographic changes in Western North America over the past 15 million years. Major rivers here are composites of different ancient rivers, resulting in isolation and mixing episodes between river basins over time. This history influenced the diversification of most of the aquatic fauna. The genus Pantosteus is one of several clades centered in this tectonically active region. The eight recognized Pantosteus species are widespread and common across southwestern Canada, western USA and into northern Mexico. They are typically found in medium gradient, middle-elevation reaches of rivers over rocky substrates. This study (1) compares molecular data with morphological and paleontological data for proposed species of Pantosteus, (2) tests hypotheses of their monophyly, (3) uses these data for phylogenetic inferences of sister-group relationships, and (4) estimates timing of divergence events of identified lineages. Using 8055 base pairs from mitochondrial DNA protein coding genes, Pantosteus and Catostomus are reciprocally monophyletic, in contrast with morphological data. The only exception to a monophyleticPantosteus is P. columbianus whose mtDNA is closely aligned with C. tahoensis because of introgression. Within Pantosteus, several species have deep genetic divergences among allopatric sister lineages, several of which are diagnosed and elevated to species, bringing the total diversity in the group to 11 species. Conflicting molecular and morphological data may be resolved when patterns of divergence are shown to be correlated with sympatry and evidence of introgression

Fishes of the Lake Eyre catchment of central Australia

Despite a defining quality of a desert being a lack of water, deserts do have water resources which maintain wildlife, especially aquatic wildlife, much of which cannot survive without permanent water. Around 70% of the land mass of Australia is considered arid and the arid areas can be separated broadly into two regions based on its fishes. The western portion includes the inland drainages from west of the Finke River near Alice Springs in the Northern Territory to the edge of the Pilbara in Western Australia. This massive area is largely unexplored for fishes partly because of its remoteness and very scant water resources. The eastern portion, now renamed the Lake Eyre Region, extends from the Finke River east to the Bulloo River at Quilpie and from Mount Isa in Queensland in the north to Broken Hill in New South Wales in the south. This region contains a fascinating assemblage of aquatic animals in a variety of habitats, including a characteristic grouping of fish (33 native species) and the fish communities are in remarkably good condition. The aquatic habitats and the aquatic flora and fauna are described and the management of fishes, wetlands and catchments is discussed. Description, habitat, biology and distribution details are provided for 13 families of fish of the Lake Eyre Region, together small colour photographs

Population genetics and dispersal of the flatworm,Polycelis coronata:a test of the habitat stability hypothesis

The habitat stability hypothesis states that species in spring-like habitats have little reason to disperse compared to species in temporary habitats. Planarians commonly inhabit springs around the world and they have long been considered poor dispersers. Recently, however, genetic analyses have shown contradictory results on the dispersal of planarians. Asexual planarians that can establish a new population by colonization of a single individual showed little genetic differentiation between sites separated by hundreds of kilometers, whereas species inhabiting springs showed deep differentiation between sites separated by hundreds of meters. The latter results are consistent with the habitat stability hypothesis. We used the cytochrome oxidase subunit I gene from 468 individuals of Polycelis coronata, an asexual species, collected from 50 sites, nested in 26 tributaries, in 4 catchments of the Wasatch Mountains of Utah, USA, to explore the dispersal capabilities of P. coronata. The longest distance between sites was 66 km. Despite this small spatial extent, we found that 77% of the 130 haplotypes were collected from a single site and 89% from a single catchment. FST values between local populations in the same tributary (0.221, 0.266, 0.389) were similar to the average FST values in different catchments for other headwater taxa. Also, variation among individuals accounted for the majority of genetic structuring with little differentiation beyond the scale of a single site. Dispersal is very slow in this species which is consistent with the habitat stability hypothesis. However, we suggest that other explanations also warrant consideration. We also identified two potential cryptic species suggesting a high degree of hidden variation at the level of species in this genus

Did Common Disjunct Populations of Freshwater Fishes in Northern Australia form from the Same Biogeographic Events?

Several freshwater fishes have disjunct (geographically discrete and widely spaced) distributions across northern Australia. We used mitochondrial deoxyribonucleic acid (mtDNA) data and phylogeographic analyses to examine the origin of these common disjunct distributions and to test the hypothesis that they were a result of a single biogeographic event. These disjunct distributions are not perfectly shared among species, but we selected 3 species that have wide ranges with the most similar disjunct geographic overlap: Spotted Blue Eye (Pseudomugil gertrudae), Pennyfish (Denariusa australis), and MacCulloch's Rainbow Fish (Melanotaenia maccullochi). Despite similarity in their present-day disjunct distributions, spatial genetic patterns varied considerably among the 3 species in terms of measures of molecular diversity, number of mtDNA lineages within each species, inter-and intra-regional spatial distribution of individual lineages within species, and degree of partitioning of genetic variation among regions. Pseudomugil gertrudae and D. australis each contained 1 to 2 divergent lineages at particular sites in 1 of the regions (Top End), but both species also contained lineages in this region that were more closely related to conspecific populations in other regions. Two regional populations (Top End and Northern Cape York Peninsula) of M. maccullochi consisted exclusively of highly divergent lineages that probably reflect cryptic species. When the divergent lineages within each species were excluded from temporal analyses, a single vicariant event among regions could not be rejected. Our results indicate that several regional populations are long-term relicts for M. maccullochi and that several sites within Top End are associated with localized long-term refugia for P. gertrudae and D. australis. A single biogeographic event in the mid-to late-Pleistocene may have created broadscale separation of most populations of these species.Full Tex